Credit: RM Chapple The history of astronomy has long been a fascination of mine, and no object in the Solar system better represents the gradual unfolding of this history than Saturn. When Galileo aimed his telescope at Saturn in 1610, he observed what he thought were two large moons on either side of the planet. But when he looked at Saturn again, two years later, the moons seemed to have mysteriously disappeared. Galileo was viewing the rings edge-on, so they were invisible to his crude telescope. Advancements in optics meant that greater details could soon be discerned. It was Huygens in 1655 who finally realized that Saturn was encircled by rings. In 1675, Cassini discovered a gap in the rings which is now known as the Cassini Division. The image below is the culmination of these observations. It is a composite taken by the Cassini spacecraft in September 2006. It shows Saturn eclipsing the sun, with the extensive ring system clearly visible. In the lower right of the picture, the Earth is faintly visible between the blue E ring and the G ring.
Credit: JPL NASA